1. Technical Field
This invention relates to a Vertical-Cavity Surface-Emitting Laser (hereinafter referred to as VCSEL) used as a light source for optical data processing or high-speed optical transmission. This invention also relates to a module, an optical transmission device, a free space optical communication device, an optical transmission system, and a free space optical communication system.
2. Related Art
In recent years, in technical fields such as optical communication or optical storage, there has been a growing interest in VCSELs. VCSELs have excellent characteristics which edge-emitting semiconductor lasers do not have. For example, a VCSEL has a lower threshold current and consumes less power. With VCSELs, a round light spot can be easily obtained, and evaluation can be performed while they are on a wafer, and light sources can be arranged in two-dimensional arrays. With these characteristics, demands for VCSELs as light sources have been expected to grow especially in the communication field.